Search for circular polarization of HCN maser emission in CIT 6

A search has been made for circular polarization of HCN maser emission in the circumstellar envelope of the carbon star CIT 6, using the 14 m FCRAO telescope. The emission has been found to be circularly unpolarized, with a 3 sigma upper limit of about 3 percent. The absence of circular polarization, together with relatively strong linear polarization detected previously, suggests a situation with the stimulated emission rate far less than the magnetic splitting far less than the line width of maser emission. The intensity of the line, as well as the degree and position angle of linear polarization, have been found to be constant on a time scale of 1 yr. 19 refs